U.S. patent number 7,798,586 [Application Number 12/070,330] was granted by the patent office on 2010-09-21 for remaining amount detection sensor and ink-jet printer using the same.
This patent grant is currently assigned to SII Printek Inc.. Invention is credited to Toshiaki Watanabe.
United States Patent |
7,798,586 |
Watanabe |
September 21, 2010 |
Remaining amount detection sensor and ink-jet printer using the
same
Abstract
Provided is a remaining amount detection sensor (4) which is
disposed outside a sub-tank (3) to detect a remaining amount of an
ink (20), including: a detection electrode (4a) disposed so as to
face the sub-tank (3); a guard electrode (4b) disposed in the same
plane as the detection electrode (4a) so as to surround an outer
periphery of the detection electrode (4a); and a guard electrode
(4d) which is disposed so as to face the detection electrode (4a)
with a space in at least a range covering the detection electrode
(4a), and has the same potential as that of the guard electrode
(4b), in which the remaining amount of the content of the sub-tank
(3) can be detected based on a capacitance to be measured by the
detection electrode (4a) with the potentials of the guard
electrodes (4b) (4d) each being set as a reference potential.
Accordingly, in the remaining amount detection sensor and the
ink-jet printer using the same, the remaining amount of the content
of the container can be detected with high accuracy.
Inventors: |
Watanabe; Toshiaki (Chiba,
JP) |
Assignee: |
SII Printek Inc.
(JP)
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Family
ID: |
39903569 |
Appl.
No.: |
12/070,330 |
Filed: |
February 14, 2008 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20090040262 A1 |
Feb 12, 2009 |
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Foreign Application Priority Data
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Feb 23, 2007 [JP] |
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2007-043651 |
Dec 4, 2007 [JP] |
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2007-313514 |
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Current U.S.
Class: |
347/7; 347/86;
347/17; 347/19; 347/14; 347/87; 73/290R |
Current CPC
Class: |
B41J
2/17566 (20130101); B41J 2/17509 (20130101); B41J
2002/17579 (20130101) |
Current International
Class: |
B41J
2/195 (20060101); B41J 2/30 (20060101); B41J
29/393 (20060101); B41J 2/175 (20060101); G01F
23/00 (20060101) |
Field of
Search: |
;347/7,14,17,19,86,87
;73/290R |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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8197749 |
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Aug 1996 |
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JP |
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9166474 |
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Jun 1997 |
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JP |
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Primary Examiner: Peng; Charlie
Assistant Examiner: Lam; Hung
Attorney, Agent or Firm: Adams & Wilks
Claims
What is claimed is:
1. A remaining amount detection sensor which is disposed outside a
container to detect a remaining amount of content of the container,
the remaining amount detection sensor comprising: a detection
electrode disposed so as to face the container; a first guard
electrode disposed in the same plane as the detection electrode so
as to surround an outer periphery of the detection electrode; and a
second guard electrode disposed so as to face the detection
electrode with a space in at least a range covering the detection
electrode, the second guard electrode having the same potential as
that of the first guard electrode; wherein the remaining amount of
the content of the container can be detected based on a capacitance
to be measured by the detection electrode with the potentials of
the first guard electrode and the second guard electrode each being
set as a reference potential.
2. An ink-jet printer comprising: an ink-jet head for discharging
ink; an ink tank for supplying the ink to the ink-jet head; and a
remaining amount detection sensor according to claim 1 disposed
outside the ink tank.
3. A remaining amount detection sensor according to claim 1;
wherein the detection electrode comprises a plurality of the
detection electrodes formed at positions spaced apart from each
other; wherein the first guard is in a state of surrounding an
outer periphery of each of the plurality of detection electrodes;
and wherein the remaining amount of the content of the container
can be detected in a plurality of levels based on capacitances to
be measured by the plurality of detection electrodes.
4. An ink-jet printer comprising: an ink-jet head for discharging
ink; an ink tank for supplying the ink to the ink-jet head; and a
remaining amount detection sensor according to claim 3 disposed
outside the ink tank.
5. A remaining amount detection sensor according to claim 3;
wherein the detection electrode, the first guard electrode, and the
second guard electrode are each formed as a conductive pattern of a
multilayer printed board; and wherein the multilayer printed board
has a remaining amount detection circuit integrally formed thereon
for measuring the capacitance of the detection electrode to
generate a remaining amount detection output.
6. A remaining amount detection sensor according to claim 3;
further comprising: a third guard electrode having the same
potential as that of each of the first guard electrode and the
second guard electrode, the third guard electrode being disposed so
as to face at least one of the first guard electrode and the second
guard electrode with a space on an opposite side of the container;
and a reference electrode disposed so as to be sandwiched in a
range in which one of the first guard electrode and the second
guard electrode, and the third electrode are opposed to each
other.
7. A remaining amount detection sensor according to claim 1;
further comprising: a third guard electrode having the same
potential as that of each of the first guard electrode and the
second guard electrode, the third guard electrode being disposed so
as to face at least one of the first guard electrode and the second
guard electrode with a space on an opposite side of the container;
and a reference electrode disposed so as to be sandwiched in a
range in which one of the first guard electrode and the second
guard electrode, and the third electrode are opposed to each
other.
8. An ink-jet printer comprising: an ink-jet head for discharging
ink; an ink tank for supplying the ink to the ink-jet head; and a
remaining amount detection sensor according to claim 7 disposed
outside the ink tank.
9. A remaining amount detection sensor according to claim 7;
wherein the detection electrode, the first guard electrode, the
second guard electrode, the third guard electrode, and the
reference electrode are each formed as a conductive pattern of a
multilayer printed board; and wherein the multilayer printed board
has a remaining amount detection circuit integrally formed thereon
for measuring the capacitance of the detection electrode to
generate a remaining amount detection output.
10. A remaining amount detection sensor according to claim 7;
wherein the second guard electrode is disposed in a range covering
each of the detection electrode and the first guard electrode;
wherein the third guard electrode is disposed in a range covering
the second guard electrode; and wherein the reference electrode is
disposed so as to be sandwiched in a range in which the second
guard electrode and the third guard electrode are opposed to each
other.
11. An ink-jet printer comprising: an ink-jet head for discharging
ink; an ink tank for supplying the ink to the ink-jet head; and a
remaining amount detection sensor according to claim 10 disposed
outside the ink tank.
12. A remaining amount detection sensor according to claim 10;
wherein the detection electrode, the first guard electrode, the
second guard electrode, the third guard electrode, and the
reference electrode are each formed as a conductive pattern of a
multilayer printed board; and wherein the multilayer printed board
has a remaining amount detection circuit integrally formed thereon
for measuring the capacitance of the detection electrode to
generate a remaining amount detection output.
13. A remaining amount detection sensor according to claim 7;
wherein the reference electrode is disposed in a range in which the
first guard electrode and the third guard electrode are opposed to
each other; and wherein the reference electrode is disposed in the
same plane as the second guard electrode.
14. An ink-jet printer comprising: an ink-jet head for discharging
ink; an ink tank for supplying the ink to the ink-jet head; and a
remaining amount detection sensor according to claim 13 disposed
outside the ink tank.
15. A remaining amount detection sensor according to claim 13;
wherein the detection electrode, the first guard electrode, the
second guard electrode, the third guard electrode, and the
reference electrode are each formed as a conductive pattern of a
multilayer printed board; and wherein the multilayer printed board
has a remaining amount detection circuit integrally formed thereon
for measuring the capacitance of the detection electrode to
generate a remaining amount detection output.
16. An ink-jet printer comprising: an ink-jet head for discharging
ink; an ink tank for supplying the ink to the ink-jet head; and a
remaining amount detection sensor according to claim 15 disposed
outside the ink tank.
17. A remaining amount detection sensor according to claim 1;
wherein the detection electrode, the first guard electrode, and the
second guard electrode are each formed as a conductive pattern of a
multilayer printed board; and wherein the multilayer printed board
has a remaining amount detection circuit integrally formed thereon
for measuring the capacitance of the detection electrode to
generate a remaining amount detection output.
18. An ink-jet printer comprising: an ink-jet head for discharging
ink; an ink tank for supplying the ink to the ink-jet head; and a
remaining amount detection sensor according to claim 17 disposed
outside the ink tank.
Description
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a remaining amount detection
sensor for detecting a remaining amount of content of a container,
and an ink-jet printer using the same.
2. Description of the Related Art
Up to now, there have been known various remaining amount detection
sensors for detecting a remaining amount of content, such as liquid
and powder, contained in a container.
For example, in an ink-jet printer for performing image recording
and the like by discharging ink from an ink-jet head, a remaining
amount of ink contained in an ink tank for supplying ink to the
ink-jet head is monitored. Then, when the ink remaining amount
decreases, ink is replenished from an ink replenishment tank, and
in a case where the ink tank is a replaceable cartridge, it is
notified that a time for replacement of the ink tank approaches.
Further, there has been known that a remaining amount detection
sensor of a capacitance type is disposed outside the ink tank,
thereby detecting the ink remaining amount.
For example, JP 08-197749A discloses an ink-jet printer which
includes an ink tank for storing conductive ink, electrodes for
outside of the container, and the two detection electrodes
sandwiching the container are affected by other conductive
structures and electrical circuits disposed on the periphery of the
detection circuit, so there arises a problem in that the
capacitance is changed due to a change in surrounding environments
and the like, and a measurement error or erroneous detection
occurs.
In particular, in the case of the ink-jet printer, the change in
capacitance of the ink tank due to the change in remaining amount
of the ink to be detected is generally extremely small.
Accordingly, the noise due to the external factors has a large
effect on the measurement accuracy.
Further, in many cases, the ink tank of the ink-jet printer is
disposed near the electrical circuit for controlling discharge of
the ink-jet head and controlling a movement mechanism and the like
of the ink-jet head, is movably held on a recording medium, and is
disposed near a movable member. As a result, an amount of noise to
be generated due to the external factors is increased.
In addition, in the ink-jet printer, ink tanks for each color are
prepared for color recording, and the ink tanks are arranged in
parallel with each other. As a result, detection electrodes for the
ink tanks for different colors are adjacent to each other. For this
reason, the capacitance is formed also between detection electrodes
of another adjacent remaining amount detection sensor, which causes
an increase in measurement error.
In order to eliminate the effects of the surrounding environments,
the remaining amount detection sensor and the ink tanks can be
disposed to be spaced apart from other members and other remaining
amount detection sensors which affect the capacitance, but there
arises another problem in that the apparatus is increased in
size.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-mentioned
problems, and therefore an object of the present invention is to
provide a remaining amount detection sensor capable of detecting a
remaining amount of content of a container with high accuracy, and
an ink-jet printer using the same.
In order to solve the problems, according to a first aspect of the
present invention, there is provided a remaining amount detection
sensor which is disposed outside a container to detect a remaining
amount of content of the container, including: a detection
electrode disposed so as to face the container; a first guard
electrode disposed in the same plane as the detection electrode so
as to surround an outer periphery of the detection electrode; and a
second guard electrode which is disposed so as to face the
detection electrode with a space in at least a range covering the
detection electrode, and has the same potential as that of the
first guard electrode, in which the remaining amount of the content
of the container can be detected based on a capacitance to be
measured by the detection electrode with the potentials of the
first guard electrode and the second electrode each being set as a
reference potential.
In the first aspect of the present invention, the detection
electrode is disposed so as to face the container. Further, the
first guard electrode surrounds the outer periphery of the
detection electrode. The second guard electrode, which has the same
potential as that of the first guard electrode, is disposed so as
to face the detection electrode with a space in at least the range
covering the detection electrode. As a result, effects of the
arrangement of the components on a side of the detection electrode
and on a rear side at which the second guard electrode is
positioned, and of an external electric field, on the capacitance
of the detection electrode can be blocked or reduced. Accordingly,
the capacitance of the container, which is positioned near the
surface of the detection electrode, and the capacitance of the
content of the container can be detected with high accuracy.
According to a second aspect of the present invention, in the
remaining amount detection sensor according to the first aspect of
the present invention, the detection electrode includes a plurality
of the detection electrodes formed at positions spaced apart from
each other; the first guard electrode is in a state of surrounding
an outer periphery of each of the plurality of detection
electrodes; and the remaining amount of the content of the
container can be detected in a plurality of levels based on
capacitances to be measured by the plurality of detection
electrodes.
In the second aspect of the present invention, the first guard
electrode is in the state of surrounding the outer periphery of
each of the plurality of detection electrodes disposed at positions
spaced apart from each other. Accordingly, each of the detection
electrodes does not affect the measurement of the capacitance by
each of the detection electrodes. The remaining amount of the
content at each arrangement position can be detected by each of the
detection electrodes, thereby making it possible to detect the
remaining amount of the content in a plurality of levels with high
accuracy.
According to a third aspect of the present invention, the remaining
amount detection sensor according to the first or the second aspect
of the present invention, further includes: a third guard electrode
which has the same potential as that of each of the first guard
electrode and the second guard electrode, and is disposed so as to
face at least one of the first guard electrode and the second guard
electrode with a space on an opposite side of the container; and a
reference electrode disposed so as to be sandwiched in a range in
which one of the first guard electrode and the second guard
electrode, and the third electrode are opposed to each other.
In the third aspect of the present invention, a reference electrode
is sandwiched in the range in which at least one of the first guard
electrode and the second guard electrode, and the third guard
electrode, thereby being shielded from the external electric field,
and is integrally formed on the side or on the rear side of the
detection part which is formed of the detection electrode and the
first and second guard electrodes. As a result, through the
measurement of the capacitance of the reference electrode, effects
of the environmental factors on the detection electrode and the
reference electrode, for example, the fluctuation of the
capacitance near the remaining amount detection sensor due to
temperature and humidity can be detected.
Accordingly, for example, by converting the fluctuation of the
capacitance detected by the reference electrode into the
fluctuation of the capacitance of the detection electrode so as to
obtain a difference therebetween, a noise component due to the
environmental factors can be eliminated.
According to a fourth aspect of the present invention, in the
remaining amount detection sensor according to the third aspect of
the present invention, the reference electrode is disposed in a
range in which the first guard electrode and the third guard
electrode are opposed to each other, and is disposed in the same
plane as the second guard electrode.
In the fourth aspect of the present invention, the reference
electrode is disposed in the same plane as the second guard
electrode. Accordingly, a thinner remaining amount detection sensor
can be formed as compared with a case of forming the reference
electrode between the second guard electrode and the third guard
electrode.
Further, when the reference electrode is disposed in the same plane
as the second guard electrode, the reference electrode and the
second guard electrode can be formed as a conductive pattern in the
same layer of the multilayer printed board, thereby making it
possible to use a multilayer printed board with a small number of
layers.
According to a fifth aspect of the present invention, in the
remaining amount detection sensor according to the third aspect of
the present invention, the second guard electrode is disposed in a
range covering each of the detection electrode and the first guard
electrode; the third guard electrode is disposed in a range
covering the second guard electrode; and the reference electrode is
disposed so as to be sandwiched in a range in which the second
guard electrode and the third guard electrode are opposed to each
other.
In the fifth aspect of the present invention, the reference
electrode is sandwiched between the second and third guard
electrode, thereby being shielded from the external electric field,
and is integrally formed on the rear surface of the detection part
formed of the detection electrode and the first and second guard
electrodes. As a result, through the measurement of the capacitance
of the reference electrode, the effects of the environmental
factors on the detection electrode and the reference electrode, for
example, the fluctuation of the capacitance near the remaining
amount detection sensor due to temperature and humidity can be
detected.
Accordingly, for example, by converting the fluctuation of the
capacitance detected by the reference electrode into the
fluctuation of the capacitance of the detection electrode so as to
obtain a difference therebetween, a noise component due to the
environmental factors can be eliminated.
In this case, the second guard electrode is formed in the region
covering the detection electrode and the first guard electrode, and
the third guard electrode is formed in the range covering the
second guard electrode, thereby more reliably reducing the effects
of the environmental factors on the detection electrode and the
reference electrode.
According to a sixth aspect of the present invention, in the
remaining amount detection sensor according to the first aspect or
the second aspect of the present invention, the detection
electrode, the first guard electrode, and the second guard
electrode are each formed as a conductive pattern of a multilayer
printed board; and the multilayer printed board has a remaining
amount detection circuit integrally formed thereon, for measuring
the capacitance of the detection electrode to generate a remaining
amount detection output.
In the sixth aspect of the present invention, the sensor part
formed of the detection electrode and the first and second guard
electrodes, and the remaining amount detection circuit are
integrally formed on the multilayer printed board. As a result, the
wiring from the detection electrode is shortened, and a remaining
amount detection sensor resistant to noise can be formed.
According to a seventh aspect of the present invention, in the
remaining amount detection sensor according to any one of the third
to fifth aspects of the present invention, the detection electrode,
the first guard electrode, the second guard electrode, the third
guard electrode, and the reference electrode are each formed as a
conductive pattern of a multilayer printed board; and the
multilayer printed board has a remaining amount detection circuit
integrally formed thereon, for measuring the capacitance of the
detection electrode to generate a remaining amount detection
output.
In the seventh aspect of the present invention, the detection
electrode, the first guard electrode, the second guard electrode,
the third guard electrode, and the reference electrode are each
formed as the conductive pattern on the multilayer printed board.
Accordingly, the sensor part formed of the detection electrode and
the first and second guard electrodes, and a reference capacitor
formed of the reference electrode sandwiched between one of the
first guard electrode and the second guard electrode, and the third
guard electrode are integrally formed, and can be integrally formed
with the remaining amount detection circuit. As a result, the
wiring from the detection electrode is shortened, and the remaining
amount detection sensor resistant to noise can be formed.
In this case, in the case of forming the remaining amount detection
circuit as a .DELTA.C-V conversion circuit, the reference electrode
enables formation of a reference capacitor resistant to noise and
environmental fluctuation. Accordingly, a compact remaining amount
detection sensor with higher accuracy can be obtained.
According to an eighth aspect of the present invention, an ink-jet
printer, includes: an ink-jet head for discharging ink; an ink tank
for supplying the ink to the ink-jet head; and the remaining amount
detection sensor according to any one of the first to seventh
aspects of the present invention, which is disposed outside the ink
tank.
In the eighth aspect of the present invention, the remaining amount
detection sensor according to any one of the first to seventh
aspects of the present invention is provided. As a result, the same
operations and effects as those described in any one of the first
to seventh aspects of the present invention are obtained.
In the remaining amount detection sensor according to the present
invention and the ink-jet printer using the same, the effects on
the capacitance of the detection electrode from the side and the
rear side thereof can be blocked or reduced. As a result, it is
possible to obtain an effect in that the remaining amount of the
content of the container, which the detection electrode faces, can
be detected with high accuracy.
BRIEF DESCRIPTION OF THE DRAWINGS
In the accompanying drawings:
FIG. 1 is an explanatory block diagram schematically showing a
general structure of an ink-jet printer using a remaining amount
detection sensor according to a first embodiment of the present
invention;
FIG. 2 is a perspective view showing an arrangement state of the
remaining amount detection sensor according to the first embodiment
of the present invention;
FIG. 3 is a perspective view showing a structure of the remaining
amount detection sensor according to the first embodiment of the
present invention;
FIG. 4 is a cross-sectional diagram of the remaining amount
detection sensor according to the first embodiment of the present
invention taken along the line A-A of FIG. 2;
FIG. 5 is a circuit diagram showing an example of a remaining
amount detection circuit for taking out an output voltage from the
remaining amount detection sensor according to the first embodiment
of the present invention;
FIG. 6 is a graph schematically showing a relation between a liquid
level position in a container and a capacitance of a detection
electrode of the remaining amount detection sensor according to the
first embodiment of the present invention;
FIG. 7A is a conceptual diagram for explaining a range, of a
capacitance to be detected by the remaining amount detection sensor
according to the embodiment of the present invention, and FIG. 7B
is a conceptual diagram for explaining a range of a capacitance to
be detected by a remaining amount detection sensor according to a
related art;
FIG. 8 is a perspective view showing a structure of a remaining
amount detection sensor according to a second embodiment of the
present invention;
FIG. 9 is a cross-sectional diagram of a side view of an
arrangement state of the remaining amount detection sensor
according to the second embodiment of the present invention;
FIGS. 10A and 10B are graphs each schematically showing a relation
between a liquid level position in a container and a capacitance of
a detection electrode of the remaining amount detection sensor
according to the second embodiment of the present invention;
FIG. 11 is an exploded perspective view showing arrangement of
electrodes of a remaining amount detection sensor according to a
third embodiment of the present invention;
FIG. 12 is across-sectional diagram of a side view of a structure
of the remaining amount detection sensor according to the third
embodiment of the present invention;
FIG. 13 is a perspective view schematically showing a general
structure of a remaining amount detection sensor according to a
modified example of the third embodiment of the present
invention;
FIG. 14 is an exploded perspective view showing arrangement of
electrodes of a remaining amount detection sensor according to a
fourth embodiment of the present invention;
FIG. 15 is a cross-sectional diagram of the remaining amount
detection sensor according to the fourth embodiment of the present
invention taken along the line B-B of FIG. 14;
FIG. 16 is an exploded perspective view showing arrangement of
electrodes of a remaining amount detection sensor according to a
fifth embodiment of the present invention;
FIG. 17 is a cross-sectional diagram of the remaining amount
detection sensor according to the fifth embodiment of the present
invention taken along the line C-C of FIG. 16;
FIG. 18 is an exploded perspective view showing arrangement of
electrodes of a remaining amount detection sensor according to a
sixth embodiment of the present invention;
FIG. 19 is a cross-sectional diagram of the remaining amount
detection sensor according to the sixth embodiment of the present
invention taken along the line D-D of FIG. 18;
FIG. 20 is an exploded perspective view showing arrangement of
electrodes of a remaining amount detection sensor according to a
seventh embodiment of the present invention; and
FIG. 21 is a cross-sectional diagram of the remaining amount
detection sensor according to the seventh embodiment of the present
invention taken along the line E-E of FIG. 20.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Hereinafter, embodiments of the present invention will be described
with reference to the accompanying drawings. In all the drawings,
identical or corresponding components in different embodiments are
denoted by the same reference symbols unless otherwise specified,
and a redundant description thereof is omitted.
First Embodiment
A description is given of a remaining amount detection sensor
according to a first embodiment of the present invention as well as
an ink-jet printer using the same.
FIG. 1 is an explanatory block diagram schematically showing a
general structure of the ink-jet printer using the remaining amount
detection sensor according to the first embodiment of the present
invention. FIG. 2 is a perspective view showing an arrangement
state of the remaining amount detection sensor according to the
first embodiment of the present invention. FIG. 3 is a perspective
view showing a structure of the remaining amount detection sensor
according to the first embodiment of the present invention. FIG. 4
is a cross-sectional diagram of the remaining amount detection
sensor according to the first embodiment of the present invention
taken along the line A-A of FIG. 2. FIG. 5 is a circuit diagram
showing an example of a remaining amount detection circuit for
taking out an output voltage from the remaining amount detection
sensor according to the first embodiment of the present
invention.
As shown in FIG. 1, an ink-jet printer 100 according to the first
embodiment of the present invention includes an ink-jet head 1, a
sub-tank 3 (ink tank), a sensor holder 5, a remaining amount
detection sensor 4, which are accommodated in a carriage 10 held so
as to be relatively movable with respect to a surface of a
recording medium (not shown), and a main tank 9 for supplying an
ink 20 to the sub-tank 3. The ink-jet printer 100 performs image
recording and the like by discharging ink droplets toward the
recording medium.
The ink-jet head 1 discharges ink droplets toward the recording
medium from a head surface 1a on which a plurality of ink nozzles
are arranged, and includes, inside thereof, known structures (not
shown) such as an ink chamber and an ink discharge mechanism using
a piezoelectric element.
The ink-jet head 1 is connected to the sub-tank 3 through an ink
tube 2 so as to be supplied with the ink 20 from the sub-tank
3.
The ink-jet head 1 is fixed at a position of a height h.sub.H from
a bottom surface 10a which is a reference surface of the carriage
10 in a height direction thereof.
The sub-tank 3 is a container for storing a certain amount of the
ink 20 as the content so as to supply the ink 20 to the ink-jet
head 1 from a position near the ink-jet head 1. For example, there
can be employed a sub-tank having a rectangular parallelepiped
outer shape made of polyethylene resin or the like with a thickness
of 1 mm.
To an upper side of the sub-tank 3 an ink tube 7 for introducing
the ink 20 from the main tank 9 is connected, and to a lower side
thereof, the ink tube 2 for supplying the stored ink 20 to the
ink-jet head 1 is connected.
The sub-tank 3 is detachably held by the sensor holder 5 which is
fixed at a predetermined position in the carriage 10, and is fixed
to be positioned with respect to the sensor holder 5 when the
sub-tank 3 is mounted thereto.
Note that, for ease of explanation, a single sub-tank 3 is
illustrated in the following description and the drawings. However,
in a case of performing color printing, a plurality of sub-tanks 3
having the same structure are arranged in parallel with each other
according to the number of colors of the ink 20.
The sensor holder 5 is a holding member for detachably fixing the
sub-tank 3 and for performing positioning of the sub-tank 3 in the
carriage 10. Inside the sensor holder 5, there is provided the
remaining amount detection sensor 4 which is urged by a pressure
spring 6 to be brought into close contact with a side surface of
the sub-tank 3 being mounted.
A height of the sensor holder 5 being mounted is set so that a
given meniscus shape is formed at the ink nozzles formed on the
head surface 1a and an ink liquid level 20a in the sub-tank 3 is
lower than the head surface 1a. In other words, a height h.sub.i of
a bottom surface 10a, which is measured from the bottom surface 10a
of the carriage 10, is represented as h.sub.i<h.sub.H.
As shown in FIG. 2, the remaining amount detection sensor 4 is
disposed outside the side surface of the sub-tank 3, and detects
the height of the ink liquid level 20a by measuring a capacitance
on a side of the sub-tank 3, thereby detecting the remaining amount
of the ink 20 contained in the sub-tank 3.
As shown in FIGS. 2 to 4, the remaining amount detection sensor 4
has a structure in which an electrode pattern which is formed of a
detection electrode 4a and a guard electrode 4b (first guard
electrode), and a guard electrode 4d (second guard electrode) are
disposed so as to face each other through a dielectric layer 4c
with a thickness d. The remaining amount detection sensor 4 has a
rectangular outer shape with a size of W.sub.1.times.H.sub.1 which
can be contained within a range of the side surface of the sub-tank
3.
The remaining amount detection sensor 4 according to the first
embodiment of the present invention is structured by using a
double-sided printed board. In other words, a conductive pattern is
formed on one substrate surface as the electrode pattern formed of
the detection electrode 4a and the guard electrode 4b, and the
guard electrode 4d is formed on the other substrate surface as a
solid pattern. In addition, a base material of the printed board
forms the dielectric layer 4c. As a material of the double-sided
printed board, for example, a glass composite substrate and a glass
epoxy substrate can be employed.
The detection electrode 4a is provided at a substantial center of
the surface on which a rectangular conductor layer with a long side
H.sub.2 and a short side W.sub.2 (note that H.sub.2<H.sub.1 and
W.sub.2<W.sub.1) is brought into close contact with the
remaining amount detection sensor 4, thereby enabling detection of
a potential via wiring (not shown). The long side of the detection
electrode 4a is placed along a height direction of the sub-tank 3,
that is, a vertical direction in which the ink liquid level 20a
rises or falls.
The guard electrode 4b is a conductive layer which is disposed in
the same plane as the detection electrode 4a so as to surround an
outer periphery of the detection electrode 4a and which is extended
to an outer edge of the remaining amount detection sensor 4, that
is, the rectangular outer shape having the size of
W.sub.1.times.H.sub.1, and is grounded via wiring (not shown).
The guard electrode 4d is a conductive layer which faces the
detection electrode 4a and the guard electrode 4b and which covers
the detection electrode 4a and the guard electrode 4b to be
extended to the outer edge of the remaining amount detection sensor
4, and is grounded via wiring (not shown).
As a result, as shown in FIG. 4, between the detection electrode 4a
and the guard electrode 4b, and between the detection electrode 4a
and the guard electrode 4d, there are formed capacitors having a
combined capacitance of C.sub.S.
As shown in FIG. 1, wiring connected to the detection electrode 4a
and a ground wire connected to each of the guard electrodes 4b and
4d are electrically connected to a remaining amount detection
circuit part 11 (remaining amount detection circuit) for detecting
the capacitance of the detection electrode 4a to thereby detect the
remaining amount in the sub-tank 3.
As long as a potential of the detection electrode 4a can be
detected with a required accuracy, the remaining amount detection
circuit part 11 may have any circuit configuration. In the first
embodiment of the present invention, as an example, a .DELTA.C-V
conversion circuit as shown in FIG. 5 is employed.
The remaining amount detection circuit part 11 according to the
first embodiment of the present invention outputs a voltage
V.sub.OUT obtained by converting, into a voltage, a difference
.DELTA.C in capacitance of a reference capacitor 31 having the
capacitance C.sub.S of the detection electrode 4a and a known
capacitance C.sub.ref. The remaining amount detection circuit part
11 includes an oscillator 30 for adding sine-wave signals to the
remaining amount detection sensor 4 and the reference capacitor 31,
a differential amplifier 32 for detecting a difference between the
signals, a rectifier 33 for rectifying an output of the
differential amplifier 32, and an amplifier 34 for amplifying the
signals rectified by the rectifier 33. As the differential
amplifier 32, there can be employed a typical operational amplifier
for comparing and calculating a voltage amplitude difference and a
voltage phase difference, which are generated between both ends of
the capacitance C.sub.S and the capacitance C.sub.ref, to output
the difference.
In the remaining amount detection circuit part 11, the voltage
V.sub.OUT corresponds to a phase difference amount which is
generated according to the difference .DELTA.C in capacitance
between the detection electrode 4a and the reference capacitor 31.
Accordingly, when C.sub.S=C.sub.ref is satisfied, V.sub.OUT=0 is
established. A value of V.sub.OUT is used to calculate the
difference .DELTA.C, and the capacitance of the detection electrode
4a can be measured assuming that C.sub.S=C.sub.ref+.DELTA.C.
In the first embodiment of the present invention, the capacitance
C.sub.ref of the reference capacitor 31 is set to a value equal to
a capacitance C.sub.S2 of the detection electrode 4a in a case
where a position in the height direction with respect to the head
surface 1a of the ink liquid level 20a in the sub-tank 3 matches an
appropriate position L2 at which the given meniscus shape is formed
at the ink nozzles of the ink-jet head 1.
The remaining amount detection circuit part 11 is electrically
connected to a pump drive control part 12 for controlling a pump-up
operation of a lift pump 8 connected to the ink tube 7, and the
output voltage V.sub.OUT is sent to the pump drive control part
12.
The pump drive control part 12 can control driving, stopping, and a
pump-up quantity of the lift pump 8 according to the position of
the ink liquid level 20a to be detected based on the output voltage
V.sub.OUT of the remaining amount detection circuit part 11.
For example, the pump drive control part 12 according to the first
embodiment of the present invention performs the control in the
following manner. When the output voltage V.sub.OUT is a negative
value, that is, when the ink liquid level 20a is lower than the
appropriate position L2, the pump drive control part 12 drives the
lift pump 8, and when the output voltage V.sub.OUT is 0 or larger,
that is, when the ink liquid level 20a reaches the appropriate
position L2, the pump drive control part 12 stops the lift pump 8.
Accordingly, when the ink-jet head 1 consumes the ink 20 to thereby
lower the ink liquid level 20a, replenishment of the ink 20 is
automatically performed, thereby constantly maintaining the ink
liquid level 20a at the appropriate position L2.
The main tank 9 is a container for storing the ink 20 used for
replenishing the ink 20, which is discharged from the ink-jet head
1 to be consumed, to the sub-tank 3, at a position apart from the
carriage 10.
The ink 20 contained in the main tank 9 is pumped up by the lift
pump 8 and is supplied to the sub-tank 3 through the ink tube
7.
Next, operations of the ink-jet printer 100 will be described
mainly about a remaining amount detection operation of the
remaining amount detection sensor 4.
FIG. 6 is a graph schematically showing a relation between the
liquid level position in the container and the capacitance of the
detection electrode of the remaining amount detection sensor
according to the first embodiment of the present invention. An axis
of abscissa represents the liquid level position and an axis of
ordinate represents the capacitance to be detected. FIG. 7A is a
conceptual diagram for explaining a range of the capacitance to be
detected by the remaining amount detection sensor according to the
embodiment of the present invention. FIG. 7B is a conceptual
diagram for explaining a range of the capacitance to be detected by
a remaining amount detection sensor according to a related art.
In the remaining amount detection sensor 4, the guard electrode 4b,
which is grounded, is disposed around the detection electrode 4a,
and the guard electrode 4d, which is grounded, is disposed in a
range covering the guard electrode 4b so as to face each of the
detection electrode 4a and the guard electrode 4b.
Accordingly, the capacitance of the detection electrode 4a on a
side of the guard electrode 4d is constant, and an electric field
outside the guard electrode 4d is shielded.
As a result, the capacitance of the detection electrode 4a is not
affected even when, for example, a positional relation with respect
to components provided outside the guard electrode 4d is changed by
the movement of the carriage 10, other movable members, and the
like. Further, even when an electrical circuit is provided near an
external surface side of the guard electrode 4d, an effect of the
electric field generated by the electrical circuit is blocked or
reduced.
On the other hand, in a space formed on the sub-tank 3 side, the
detection electrode 4a is adjacent to the guard electrode 4b
through the sub-tank 3 and the ink 20 contained in the sub-tank
3.
For this reason, in the remaining amount detection sensor 4, the
capacitance of the detection electrode 4a is affected only by a
change of a dielectric body provided in the space formed on the
sub-tank 3 side near the surface of the detection electrode 4a, as
shown in a region P indicated by the alternate long and two short
dashes line of FIG. 7A.
Accordingly, effects of various noises can be reduced, thereby
making it possible to measure the capacitance near the detection
electrode 4a with high accuracy.
For example, as in a comparative example of the related art shown
in FIG. 7B, when a reference electrode 50b and a detection
electrode 50a, which are grounded, are disposed in the height
direction on the side surface of the sub-tank 3 to measure the
capacitance C.sub.S of the detection electrode 50a, the capacitance
of the detection electrode 50a is affected by peripheral dielectric
bodies provided therearound in almost all the directions.
Accordingly, as shown within a range of a region Q, the capacitance
of the detection electrode 50a is affected also by the dielectric
body provided outside the sub-tank 3 to the same degree as the
sub-tank 3 and the dielectric body inside the sub-tank 3.
As a result, unlike the case of the first embodiment of the present
invention, for example, when the positional relation with respect
to the components provided outside the detection electrode 50a is
changed by the movement of the carriage 10, other movable members,
and the like, the capacitance of the detection electrode 50a is to
be changed. In addition, the detection electrode 50a is affected
also by the electric field of the electrical circuit disposed near
the detection electrode 50a because the electric field outside the
detection electrode 50a is not shielded.
As shown in FIG. 4, in the sub-tank 3, when the liquid level is
changed from a height L1 to a height L3 (L3>L1) substantially
corresponding to a height range of the long side of the detection
electrode 4a, the capacitance is increased according to the rise of
the ink liquid level 20a. For example, as represented by a curve
200 shown in FIG. 6, while the ink liquid level 20a is changed from
L1 to L2 to L3, the capacitance is substantially linearly and
monotonously increased from C.sub.S1 to C.sub.S2 to and
C.sub.S3.
As a specific numerical example, the range of the capacitance to be
detected by the remaining amount detection sensor 4 is, for
example, a range from C.sub.S1=28 pF to C.sub.S3=55 pF in the
following case. That is, for example, in a case where there is used
the remaining amount detection sensor 4 which includes the
dielectric layer 4c made of resin-impregnated glass fiber of d=1
mm, has the detection electrode 4a and the guard electrodes 4b and
4d each formed of copper foil having a thickness of 35 .mu.m, has
an outer shape of W.sub.1.times.H.sub.1=50 mm.times.50 mm, and has
the detection electrode 4a formed with a size of
W.sub.2.times.H.sub.2=16 mm.times.38 mm at a central position
thereof (that is, a=16 mm and b=5 mm in FIG. 3), and in a case
where the sub-tank 3 is made of polyethylene having a wall
thickness of 1 mm and contains aqueous ink.
The remaining amount detection sensor 4 according to the first
embodiment of the present invention can detect, as the output
voltage V.sub.OUT of the remaining amount detection circuit part
11, the change in capacitance of the detection electrode 4a, which
corresponds to the height of the ink liquid level 20a. In addition,
the remaining amount detection sensor 4 can perform control such
that the pump drive control part 12 drives the lift pump 8 so that
the output voltage V.sub.OUT becomes c{hacek over (o)}nstant, and
so that the height of the ink liquid level 20a in the sub-tank 3 is
set to the appropriate position L2.
In this case, the amount of the ink 20 to be discharged from the
ink-jet head 1 is extremely small, and the change in capacitance
due to fluctuation of the ink liquid level 20b is also extremely
small. However, in the first embodiment of the present invention,
measurement noise can be reduced, with the result that a liquid
level control can be performed with accuracy.
Accordingly, even when the ink 20 is consumed by the ink-jet head
1, the height of the ink liquid level 20a in the sub-tank 3 can be
stably maintained at the appropriate position L2. As a result, a
stable meniscus can be formed at the ink nozzles of the excellent
ink-jet head 1 and excellent image recording can be performed.
Second Embodiment
A description is given of a remaining amount detection sensor
according to a second embodiment of the present invention.
FIG. 8 is a perspective view showing a structure of the remaining
amount detection sensor according to the second embodiment of the
present invention. FIG. 9 is a cross-sectional diagram of a side
view of an arrangement state of the remaining amount detection
sensor according to the second embodiment of the present invention.
FIGS. 10A and 10B are graphs each schematically showing a relation
between a liquid level position in a container and a capacitance of
a detection electrode of the remaining amount detection sensor
according to the second embodiment of the present invention. An
axis of abscissa represents the liquid level position and an axis
of ordinate represents the capacitance to be detected.
As shown in FIGS. 8 and 9, a remaining amount detection sensor 4A
according to the second embodiment of the present invention
includes detection electrodes 40a and 40b in place of the detection
electrode 4a of the remaining amount detection sensor 4 of the
first embodiment, and a guard electrode 40c (second guard
electrode) in place of the guard electrode 4b.
As shown in FIG. 1, for example, the remaining amount detection
sensor 4A is disposed outside the side surface of the main tank 9
in the ink-jet printer 100 of the first embodiment, and measures
the capacitance on the main tank 9 side to detect whether a height
of an ink liquid level 20b is within a predetermined range, thereby
detecting the remaining amount of the ink 20 contained in the main
tank 9.
Hereinafter, the differences from the first embodiment will be
mainly described.
The detection electrodes 40a and 40b are rectangular conductive
layers, each of which has a long side W.sub.3 and a short side
H.sub.3, and which are arranged in parallel with each other with a
distance H.sub.4 (note that 2H.sub.3+H.sub.4<H.sub.1 and
W.sub.3<W.sub.1) and are provided on a surface to be brought
into close contact with the remaining amount detection sensor 4A,
thereby enabling detection of a potential via wiring (not shown).
The short side of each of the detection electrodes 40a and 40b is
placed along a height direction of an object whose remaining amount
is to be detected of, for example, the main tank 9, that is, a
vertical direction in which the ink liquid level 20b rises or falls
(see FIG. 9).
The guard electrode 40c is a conductive layer which is disposed in
the same plane as the detection electrodes 40a and 40b so as to
surround an outer periphery of each of the detection electrodes 40a
and 40b, is extended to an outer edge of the remaining amount
detection sensor 4A, that is, a rectangular outer shape with a size
of W.sub.1.times.H.sub.1, and is grounded via wiring (not
shown).
Accordingly, as shown in FIG. 9, between the detection electrodes
40a and 40b and the guard electrodes 40c and 4d, there are formed
capacitors having combined capacitances C.sub.a and C.sub.b,
respectively.
The capacitances C.sub.a and C.sub.b can be measured using an
electrical circuit similar to the remaining amount detection
circuit part 11 of the first embodiment.
The remaining amount detection sensor 4A with the above-mentioned
structure has the same structure as that in which the remaining
amount detection sensors 4 of the first embodiment are arranged in
parallel with each other in a vertical direction to be integrated
with each other.
Accordingly, in the same manner as in the detection electrode 4a of
the first embodiment, the capacitance of the detection electrode
40a (40b) is affected only by the change of the dielectric body
provided in the space formed on the sub-tank 3 side near the
surface of the detection electrode 40a (40b) as shown in a region
P.sub.a (P.sub.b) indicated by the alternate long and two short
dashes line of FIG. 9.
Accordingly, when it is assumed that a height of the ink liquid
level 20b near a lower end position of the detection electrode 40a
and a height thereof near an upper end position of the detection
electrode 40a are set as L1 and L2, respectively, and when it is
assumed that a height of the ink liquid level 20b near a lower end
position of the detection electrode 40b and a height thereof near
an upper end position of the detection electrode 40b are set as L3
and L4, respectively, the capacitance of each of the detection
electrodes 40a and 40b is changed as indicated by a curve 201 of
FIG. 10A and a curve 202 of FIG. 10B.
Specifically, when the ink liquid level 20b is lower than the
height L3, the capacitance of the detection electrode 40b is
measured as a relatively small value C.sub.b1 because the ink 20
does not enter the region P.sub.b. When the ink liquid level 20b is
positioned between the heights L3 and L4, the capacitance is
substantially linearly increased from C.sub.b1 to C.sub.b2
according to the height of the ink liquid level 20b. When the ink
liquid level 20b is equal to or higher than the height L4, the ink
20 is filled in the entire detection range of the detection
electrode 40b, with the result that a constant value C.sub.b2 is
measured.
In a similar manner, when the height of the ink liquid level 20b is
positioned between the heights L1 and L2, the capacitance of the
detection electrode 40a is substantially linearly increased from
C.sub.a1 to C.sub.a2, and when the height is equal to or higher
than the height L2, a constant value C.sub.a2 is measured.
Thus, according to the remaining amount detection sensor 4A, a
magnitude of the capacitance of each of the detection electrodes
40b and 40a is analyzed, thereby making it possible to detect the
positional relation of the ink liquid level 20b with respect to the
four heights L1, L2, L3, and L4 corresponding to the arrangement
positions of the detection electrodes 40b and 40a in the height
direction. For example, when the capacitances of the detection
electrodes 40b and 40a are C.sub.b1 and C.sub.a2, respectively, it
can be detected that the ink liquid level 20b is positioned between
the heights L2 and L3.
In particular, in a height range from L1 to L2, and in a height
range from L3 to L4, by the use of the capacitance of each of the
detection electrodes 40b and 40a, the height of the ink liquid
level 20b can be measured.
In this case, in the same manner as in the first embodiment, the
effects of various noises are reduced, thereby making it possible
to measure the capacitances near the detection electrode 40a and
40b with high accuracy.
The remaining amount detection sensor 4A singly includes a
plurality of detection electrodes. Accordingly, for example, the
remaining amount detection sensor 4A can detect the ink liquid
level 20b in the main tank 9, to thereby singly detect whether the
remaining amount of the ink 20 contained in the main tank 9 is
within the range of the predetermined amount with reliability. When
the liquid level of the ink liquid level 20b is lower than the
height L2, a reduction amount can be detected with accuracy. As a
result, by the use of a detection output, an ink remaining amount
can be displayed, and alarm display for urging a user to replenish
ink can be performed.
Further, when the ink 20 is replenished to the main tank 9, through
detection of the height of the ink liquid level 20b, a warning of
proximity of a limit of a replenishment amount can be issued.
Third Embodiment
A description is given of a remaining amount detection sensor
according to a third embodiment of the present invention.
FIG. 11 is an exploded perspective view showing arrangement of
electrodes of the remaining amount detection sensor according to
the third embodiment of the present invention. FIG. 12 is a
cross-sectional diagram of a side view of a structure of the
remaining amount detection sensor according to the third embodiment
of the present invention.
As shown in FIGS. 11 and 12, a remaining amount detection sensor 4B
according to the third embodiment of the present invention includes
a guard electrode 41e (third guard electrode), a reference
electrode 41a, and a dielectric layer 41b, in addition to a
detection part 41A which is structured in the same manner as the
remaining amount detection sensor 4 of the first embodiment.
The guard electrode 41e is a conductive layer having the same shape
and made of the same material as the guard electrode 4d, is
disposed so as to face the guard electrode 4d on an opposite side
of the detection electrode 4a, and is grounded via wiring (not
shown).
Between the guard electrode 4d and the guard electrode 41e, the
dielectric layer 41b made of the same material as that of the
dielectric layer 4c is disposed.
The reference electrode 41a is formed of a conductive layer having
an area smaller than that of each of the guard electrodes 4d and
41e, and is disposed in the dielectric layer 41b at an intermediate
position in a direction in which the guard electrodes 4d and 41e
are spaced apart, and at a substantial center between surface
directions of the guard electrodes 4d and 41e, thereby making it
possible to detect the potential via wiring (not shown).
The area of the reference electrode 41a, the distance between the
guard electrodes 4d and 41e, and the like are set so that the
capacitance of the reference electrode 41a is set to the constant
value C.sub.ref.
Thus, in the remaining amount detection sensor 4B, the detection
part 41A serving as a capacitor showing the capacitance C.sub.S
corresponding to the peripheral dielectric body, and the reference
part 41B serving as a capacitor having the constant capacitance
C.sub.ref are integrated in layers.
Accordingly, the remaining amount detection sensor 4B according to
the third embodiment of the present invention can be formed of a
multilayer printed board with the detection electrode 4a, the guard
electrode 4b, and the guard electrodes 4d and 41e each being used
as the electrode pattern. In this case, the dielectric layer 41b is
formed of a base material of the multilayer printed board.
In the remaining amount detection sensor 4B with the
above-mentioned structure, the reference part 41B is integrated
with the detection part 41A and serves as a capacitor made of the
same material as that of the detection part 41A. Accordingly, the
capacitance C.sub.ref can be formed in the same order as that of
the capacitance C.sub.S of the detection part 41A merely by
changing the area of the reference electrode 41a, the thickness of
the dielectric layer 41b, and the like to a small extent in an
analog manner.
For this reason, for example, it is extremely easy to obtain,
through an experiment or the like, a capacitance in a case where
the detection electrode 4a is disposed at a detection position of
the sub-tank 3 and the ink liquid level 20a is positioned at the
appropriate height, and to set the capacitance C.sub.ref to a value
which exactly matches the measured value.
The reference part 41B thus set can be used in place of the
reference capacitor 31 of the remaining amount detection circuit
part 11 of the first embodiment.
In this case, because the reference part 41B is integrated with the
detection part 41A and is made of the same material as that of the
detection part 41A, the reference part 41B is to be changed in the
same manner as the detection part 41A when the capacitance is
changed due to a change in environmental conditions, for example, a
change in temperature and humidity. As a result, even when the
environmental conditions are changed, the difference .DELTA.C in
capacitance between the detection part 41A and the reference part
41B is obtained in a state where effects of the environmental
conditions are cancelled, and the difference .DELTA.C can be
measured with high accuracy.
On the other hand, as in the first embodiment, in the case of using
the reference capacitor 31 disposed at a position apart from the
remaining amount detection sensor 4 and having a structure
different from that of the remaining amount detection sensor 4, if
the value of C.sub.ref can be set so as to be exactly matched with
the value of C.sub.S in the appropriate condition, when the
environmental conditions are changed, the remaining amount
detection sensor 4 and the reference capacitor 31, which are made
of different materials and have different structures, are
individually changed in capacitance. As a result, a detection error
of .DELTA.C becomes larger than that in the case of using the
remaining amount detection sensor 4B according to the third
embodiment of the present invention.
Next, modified examples of the embodiments will be described.
FIG. 13 is a perspective view schematically showing a general
structure of a remaining amount detection sensor according to a
modified example of the third embodiment of the present
invention.
In a remaining amount detection sensor 4C according to the modified
example of the present invention, a sensor part 42 having the same
structure as that of the remaining amount detection sensor 4B
according to the third embodiment is formed on a part of the
multilayer printed board, and a remaining amount detection circuit
part 43 (remaining amount detection circuit) is formed on the board
on a side adjacent to the sensor part 42.
The remaining amount detection circuit part 43 can employ a
structure using the reference part 41B as the reference capacitor
31 in the remaining amount detection circuit part 11 according to
the first embodiment.
In the remaining amount detection sensor 4C according to the
modified example, the remaining amount detection circuit part 43 is
adjacent to and integrated with the sensor part 42. As a result,
the wiring from each of the detection electrode 4a and the
reference electrode 41a to the remaining amount detection circuit
part 43 can be shortened and can be easily shielded by the use of
the wiring pattern of the multilayer board, and signal degradation
and noise contamination via the wiring can be reduced.
Accordingly, in combination with the operational effects described
in the first and third embodiments, a highly accurate and compact
remaining amount detection sensor can be obtained.
In this case, the remaining amount detection circuit part 43 may be
disposed at any position as long as the position does not affect
the capacitance of the detection electrode 4a and the capacitance
of the reference electrode 41a. In the modified example, the
remaining amount detection circuit part 43 is formed on a substrate
layer on an opposite side of the detection electrode 4a with
respect to the guard electrode 4d on the lateral side of the sensor
part 42.
In this case, the effect of the electric field of the remaining
amount detection circuit part 43 with respect to the detection
electrode 4a can be blocked by the guard electrode 4d.
The remaining amount detection sensor 4C according to the third
embodiment is an example of a remaining amount detection sensor
with a four-layered structure in which the guard electrode 4d is
disposed on a rear side (opposite side of container) of the
detection electrode 4a and the guard electrode 4b, and the
reference electrode 41a and the guard electrode 41e are also
disposed on the rear side thereof.
In other words, the remaining amount detection sensor 4C is an
example of a remaining amount detection sensor including the third,
guard electrode which is set to the same potential as that of each
of the first and second guard electrodes and which is disposed so
as to face the second guard electrode with a space on the opposite
side of the container, and the reference electrode which is
disposed so as to be sandwiched in the range in which the second
guard electrode and the third electrode are opposed to each other.
The reference electrode is integrally formed on the rear side of
the detection part which is formed of the detection electrode and
the first and second guard electrodes, whereby the reference
electrode is integrated with the detection electrode so as to be
set in substantially the same environmental conditions.
Note that, in the case of the multilayer printed board, the
dielectric layer 41b is generally joined through a thin joining
layer along the reference electrode 41a. In the schematic diagram
of FIG. 12, the joining layer is omitted (similarly in
cross-sectional diagram mentioned below).
Fourth Embodiment
A description is given of a remaining amount detection sensor
according to a fourth embodiment of the present invention.
FIG. 14 is an exploded perspective view showing arrangement of
electrodes of the remaining amount detection sensor according to
the fourth embodiment of the present invention. FIG. 15 is a
cross-sectional diagram of the remaining amount detection sensor
according to the fourth embodiment of the present invention taken
along the line B-B of FIG. 14.
As shown in FIGS. 14 and 15, a remaining amount detection sensor 4D
according to the fourth embodiment of the present invention
includes a guard electrode 44b (first guard electrode), a guard
electrode 44d (second guard electrode), and a reference electrode
44e in place of the guard electrodes 4b and 4d and the reference
electrode 41a of the remaining amount detection sensor 4C of the
third embodiment. Hereinafter, the differences from the above
embodiments will be mainly described.
The guard electrode 44b is obtained by shifting an opening of the
guard electrode 4b of the third embodiment in a short side
direction of the detection electrode 4a, and has an outer shape
with the same size as that of the guard electrode 4b. The guard
electrode 44b is formed so as to surround the outer periphery of
the detection electrode 4a in the same plane as the detection
electrode 4a.
On the rear side of the detection electrode 4a and on the rear side
(opposite side of container) of the guard electrode 44b, the guard
electrode 44d and the reference electrode 44e are disposed,
respectively, through the dielectric layer 4c.
In this case, the detection electrode 4a is disposed at a position
apart from the center of the guard electrode 44b, and the guard
electrode 44d is disposed on the rear side of the detection
electrode 4a and disposed at least in a range covering the
detection electrode 4a.
Further, the reference electrode 44e is formed in a rectangle shape
extending in the same direction as the guard electrode 4b, and is
formed with a size capable of being covered with the guard
electrode 44b. In addition, the reference electrode 44e is disposed
on a lateral side of the guard electrode 44d in parallel with each
other.
In at least the range covering the reference electrode 44e on the
rear side of the reference electrode 44e, the guard electrode 41e
is disposed so as to face the reference electrode 44e in parallel
with each other through the dielectric layer 41b. Thus, in the
fourth embodiment of the present invention, the guard electrode 41e
also covers the entirety of the guard electrode 44d.
Accordingly, the outer shape of the remaining amount detection
sensor 4D is a rectangle shape with a size of W.sub.1.times.H.sub.1
which can be contained within the range of the side surface of the
sub-tank 3.
The remaining amount detection sensor 4D according to the fourth
embodiment of the present invention is formed using a three-layered
multilayer printed board. In other words, the detection electrode
4a and the guard electrode 44b are formed by a first layer
conductive pattern, the guard electrode 44d and the reference
electrode 44e are formed by a second layer conductive pattern, and
the guard electrode 41e is formed by a third layer conductive
pattern (solid pattern).
Further, the dielectric layer 4c is formed of an insulating layer
between the first layer conductive pattern and the second layer
conductive pattern. The dielectric layer 41b is formed of an
insulating layer between the second layer conductive pattern and
the third layer conductive pattern.
Note that the structure of the remaining amount detection sensor 4D
is not limited to the structure of a single multilayer printed
board. For example, the remaining amount detection sensor 4D may be
structured by bonding a single-sided printed board and a
double-sided printed board together with an adhesive to form a
lamination structure having three conductive pattern layers.
The guard electrodes 44b, 44d, and 41e are each grounded via wiring
(not shown), and are each set to the same potential. As shown in
FIG. 15, between the detection electrode 4a and the guard electrode
44b, and between the detection electrode 4a and the guard electrode
44d, there are formed capacitors having the combined capacitance of
C.sub.S. In addition, between the reference electrode 44e and the
guard electrode 44b, and between the reference electrode 44e and
the guard electrode 41e, there are formed reference capacitors
having the combined capacitance of C.sub.ref.
Wiring connected to the detection electrode 4a, wiring connected to
the reference electrode 44e, and a ground wire connected to each of
the guard electrodes 44b, 44d, and 41e are each electrically
connected to a remaining amount detection circuit (not shown) for
detecting the capacitance of the detection electrode 4a to thereby
detect the remaining amount in the sub-tank 3
Note that the area of the reference electrode 44e, the distance
between the guard electrodes 44d and 41e, and the like are set so
that the capacitance of the reference electrode 44e is set to the
constant value C.sub.ref.
As described above, in the remaining amount detection sensor 4D,
the detection part 44A serving as a capacitor showing the
capacitance C.sub.S corresponding to the peripheral dielectric
body, and the reference part 44B serving as a capacitor having the
constant capacitance C.sub.ref are formed in an integrated manner.
In other words, the reference part 44B integrated with the
detection part 44A serves as a capacitor made of the same material
as that of the detection part 44A. For this reason, the capacitance
C.sub.ref can be formed in the same order as that of the
capacitance C.sub.S of the detection part 44A merely by changing
the area of the reference electrode 44e, the thicknesses of the
dielectric layers 4c and 41b, and the like to a small extent in an
analog manner.
Accordingly, for example, it is extremely easy to obtain, through
an experiment or the like, a capacitance in a case where the
detection electrode 44a is formed at a detection position for the
sub-tank 3 and the ink liquid level 20a is positioned at the
appropriate height, and to set the capacitance C.sub.ref to a value
which exactly matches the measured value.
The reference part 44B thus set can be used in place of the
reference capacitor 31 of the remaining amount detection circuit
part 11 according to the first embodiment, and the same effects as
those of the third embodiment can be obtained.
Further, since the guard electrode 44d and the reference electrode
44e are formed in the same plane, in the case of forming the
detection electrode 4a, the guard electrodes 44b, 44d, and 41e, and
the reference electrode 44e by the conductive pattern of the
multilayer printed board, the guard electrode 44d and the reference
electrode 44e are formed by the conductive pattern in the same
layer. As a result, the number of layers of the multilayer printed
board can be reduced.
In order to reduce the effects of the environmental conditions on
the remaining amount detection accuracy of the remaining amount
detection sensor 4D, it is preferable that the detection part 44A
and the reference part 44B be disposed under substantially the same
environmental conditions.
In order to achieve this, the position of the reference electrode
44e in a width W.sub.1 direction is preferably set to a position
close to the detection electrode 4a to an extent that the reference
electrode 44e is not affected by the capacitor formed of the
detection electrode 4a and the guard electrode 44d. Further, a
length of the reference electrode 44e in a long side direction is
preferably set to a length equivalent to that of the guard
electrode 44b.
The remaining amount detection sensor 4D according to the fourth
embodiment is an example of a remaining amount detection sensor
with a three-layered structure in which the guard electrode 44d is
disposed on the rear side of the detection electrode 4a, and the
reference electrode 44e is disposed so as to face the guard
electrode 44b at a position in the same plane as the guard
electrode 44d which is disposed on a side, thereof.
In other words, the remaining amount detection sensor 4D is an
example of a remaining amount detection sensor including the third
guard electrode which is set to the same potential as that of each
of the first and second guard electrodes and which is disposed so
as to face the first guard electrode with a space on the opposite
side of the container, and the reference electrode which is
disposed so as to be sandwiched in the range in which the first
guard electrode and the third guard electrode are opposed to each
other. The reference electrode is integrally formed on the lateral
side of the detection part which is formed of the detection
electrode and the first and second guard electrodes, whereby the
reference electrode is integrated with the detection electrode so
as to be set in substantially the same environmental
conditions.
Fifth Embodiment
A description is given of a remaining amount detection sensor
according to a fifth embodiment of the present invention.
FIG. 16 is an exploded perspective view showing arrangement of
electrodes of the remaining amount detection sensor according to
the fifth embodiment of the present invention. FIG. 17 is a
cross-sectional diagram of the remaining amount detection sensor
according to the fifth embodiment of the present invention taken
along the line C-C of FIG. 16.
As shown in FIGS. 16 and 17, a remaining amount detection sensor 4E
according to the fifth embodiment of the present invention is a
generally widely used four-layered printed board in which a sensor
part 45A, which has the same structure as that of the fourth
embodiment, and a remaining amount detection circuit part 45B are
integrated with each other. In this case, the structure of the
sensor part 45A is completely the same as that of the remaining
amount detection sensor 4D according to the fourth embodiment, so a
description thereof is omitted.
Specifically, as shown in FIG. 17, in the remaining amount
detection sensor 4E according to the fifth embodiment of the
present invention, the detection electrode 4a and the guard
electrodes 44b, 44d, 44e, and 41e of the sensor part 45A are formed
by first to third layer conductive patterns of the four-layered
printed board, and a fourth layer conductive pattern 45h is used
for printed wiring for forming the detection circuit part 45B. A
circuit part 45i is mounted in the conductive pattern 45h, and a
side of the sensor part 45A and a side of the detection circuit
part 45B are connected to each other via a through hole 45j or the
like, for example, whereby the sensor part 45A and the detection
circuit part 45B are laminated to be integrated with each other in
substantially the same area range. With this structure, it is
unnecessary to form the remaining amount detection circuit part 43
by extending the printed board as shown in FIG. 13. As a result, a
projected area of the printed board is reduced, and a compact
structure can be obtained at low cost.
Sixth Embodiment
A description is given of a remaining amount detection sensor
according to a sixth embodiment of the present invention.
FIG. 18 is an exploded perspective view showing arrangement of
electrodes of the remaining amount detection sensor according to
the sixth embodiment of the present invention. FIG. 19 is a
cross-sectional diagram of the remaining amount detection sensor
according to the sixth embodiment of the present invention taken
along the line-D-D of FIG. 18.
As shown in FIGS. 18 and 19, a remaining amount detection sensor 4F
according to the sixth embodiment of the present invention
includes, in the remaining amount detection sensor 4D according to
the fourth embodiment, a guard electrode 4b (first guard electrode)
in place of the guard electrode 44b, and a pair of reference
electrodes 46e in place of the reference electrode 44e.
Hereinafter, the differences from the above embodiments will be
mainly described.
In the remaining amount detection sensor 4F, the detection
electrode 4a is disposed at the center of the guard electrode 4b in
the width direction as in the first embodiment. Further, on the
rear side (opposite side of container) of the detection electrode
4a, the guard electrode 44d is disposed through the dielectric
layer 4c as in the fourth embodiment.
The detection electrode 4a is disposed at the center of the guard
electrode 4b, whereby the two reference electrodes 46e are disposed
through the dielectric layer 4c in a range covered with the guard
electrode 4b on the rear side of the guard electrode 4b in spaces
formed on both lateral sides of the guard electrode 44d. In
addition, on the rear side of each of the reference electrodes 46e
and on the rear side of the guard electrode 44d, the guard
electrode 41e is disposed through the dielectric layer 41b.
The reference electrodes 46e each have dimensions obtained by
dividing into two the reference electrode 44e according to the
fourth embodiment in the width direction, and are each set to the
same potential via wiring (not shown).
The guard electrodes 4b, 44d, and 41e are each grounded via wiring
(not shown), and are each set to the same potential. As shown in
FIG. 19, between the detection electrode 4a and the guard electrode
4b, and between the detection electrode 4a and the guard electrode
44d, there are formed capacitors having the combined capacitance of
C.sub.S. In addition, between the reference electrode 46e and the
guard electrode 4b, and between the reference electrode 46e and the
guard electrode 41e, there are formed reference capacitors having
the combined capacitance of C.sub.ref.
In the remaining amount detection sensor 4F with the
above-mentioned structure, a detection part 46A having the same
capacitance as that of the detection part 44A according to the
fourth embodiment is formed, and reference parts 46B each serving
as a reference capacitor having the same capacitance as that of the
reference part 44B according to the fourth embodiment are formed on
both lateral sides of the detection part 46A.
Accordingly, the measurement as to the remaining amount detection
can be performed in the same manner as in the fourth
embodiment.
In this case, the reference parts 46B are formed on both lateral
sides of the detection part 46A, so the environmental conditions on
the both lateral sides of the detection electrode 4a in a traverse
direction affect each of the reference parts 46B in almost the same
manner. As a result, even when the environmental conditions are
different on both lateral sides of the detection part 46A, the
effects on the detection accuracy of the remaining amount detection
can be reduced. Accordingly, the remaining amount detection can be
performed with high accuracy.
Seventh Embodiment
A description is given of a remaining amount detection sensor
according to a seventh embodiment of the present invention.
FIG. 20 is an exploded perspective view showing arrangement of
electrodes of the remaining amount detection sensor according to
the seventh embodiment of the present invention. FIG. 21 is a
cross-sectional diagram of the remaining amount detection sensor
according to the seventh embodiment of the present invention taken
along the line E-E of FIG. 20.
As shown in FIGS. 20 and 21, a remaining amount detection sensor 4G
according to the seventh embodiment of the present invention
includes a reference electrode 47e having a rectangular loop shape
surrounding the outer periphery of the guard electrode 44d, in
place of the pair of reference electrodes 46e of the remaining
amount detection sensor 4F according to the sixth embodiment.
Hereinafter, the differences from the sixth embodiment will be
mainly described.
The reference electrode 47e is formed so that the combined
capacitance formed between the guard electrodes 4b and 41e opposed
to each other is set to the same capacitance C.sub.ref as that of
the pair of reference electrodes 46e according to the sixth
embodiment. As a result, the reference part 47B is formed so as to
surround the detection part 47A similar to the detection part 46A
on the outer peripheral side.
Accordingly, the measurement as to the remaining amount detection
can be performed in the same manner as in the sixth embodiment.
In this case, the reference part 47B surrounds the outer peripheral
side of the detection part 47A, so the environmental conditions of
the outer peripheral portion of the detection electrode 4a affect
the reference parts 47B in almost the same manner. As a result,
even when the environmental conditions are different on the outer
peripheral portion of the detection part 47A, the effects on the
detection accuracy of the remaining amount detection can be
reduced. Accordingly, the remaining amount detection can be
performed with high accuracy.
Note that the components described in the above embodiments and
modified examples can be used in appropriate combination thereof
within the technical idea of the present invention, as long as the
combination is possible from the technical point of view.
For example, the remaining amount detection sensor 4 according to
the first embodiment may be used for detecting a remaining amount
of ink contained in the main tank 9.
Further, the remaining amount detection sensor 4 may be formed of a
multilayer printed board, or the remaining amount detection circuit
part 11 may be formed on the same board. The reference capacitor 31
has a structure different from that of the remaining amount
detection sensor 4, so the effects of the environmental fluctuation
vary, but the wiring is shortened, thereby obtaining a remaining
amount detection sensor resistant to noise.
Further, in place of the remaining amount detection sensor 4 of the
ink-jet printer 100 according to the first embodiment, the
remaining amount detection sensors 4D, 4E, 4F, and 4G according to
the fourth to seventh embodiments, respectively, can be used. The
structures for arrangement of the electrodes of the remaining
amount detection sensors can be applied also to the remaining
amount detection sensor 4A according to the second embodiment.
Further, in the descriptions as to the third to seventh
embodiments, there is illustrated an example where the remaining
amount detection sensors 4D, 4E, 4F, and 4G are each formed by
using the three-layered multilayer printed board so as to minimize
the number of layers of the conductive patterns. However, in a case
where more layers of the conductive pattern can be formed, the
second guard electrode and the reference electrode are not
necessarily formed in the same plane.
In this case, depending on a position of the second guard electrode
and a difference in dielectric constant of the dielectric layer,
each capacitance of the reference parts can be changed. In such a
case, the area of the second guard electrode or the like is
appropriately set, thereby easily setting the combined capacitance
to the C.sub.ref similar to that of the above: embodiments.
Further, in the above description, the remaining amount detection
sensor is described as an example used for an ink-jet printer. This
is only an example, and the remaining amount detection sensor may
be used for detection of a remaining amount of content of a
container for an apparatus used for every purpose as long as the
remaining amount of the content of the container can be detected by
a change in capacitance.
Further, in the above description, the example where the content of
the container is a liquid is illustrated, but the content is not
limited to the liquid. The present invention may be used to detect
a remaining amount of powder, for example.
* * * * *